title: A new type of Na(+)-driven ATP synthase membrane rotor with a two-carboxylate ion-coupling motif.
abstract: The anaerobic bacterium Fusobacterium nucleatum uses glutamate decarboxylation to generate a transmembrane gradient of Na⁺. Here, we demonstrate that this ion-motive force is directly coupled to ATP synthesis, via an F₁F₀-ATP synthase with a novel Na⁺ recognition motif, shared by other human pathogens. Molecular modeling and free-energy simulations of the rotary element of the enzyme, the c-ring, indicate Na⁺ specificity in physiological settings. Consistently, activity measurements showed Na⁺ stimulation of the enzyme, either membrane-embedded or isolated, and ATP synthesis was sensitive to the Na⁺ ionophore monensin. Furthermore, Na⁺ has a protective effect against inhibitors targeting the ion-binding sites, both in the complete ATP synthase and the isolated c-ring. Definitive evidence of Na⁺ coupling is provided by two identical crystal structures of the c₁₁ ring, solved by X-ray crystallography at 2.2 and 2.6 Å resolution, at pH 5.3 and 8.7, respectively. Na⁺ ions occupy all binding sites, each coordinated by four amino acids and a water molecule. Intriguingly, two carboxylates instead of one mediate ion binding. Simulations and experiments demonstrate that this motif implies that a proton is concurrently bound to all sites, although Na⁺ alone drives the rotary mechanism. The structure thus reveals a new mode of ion coupling in ATP synthases and provides a basis for drug-design efforts against this opportunistic pathogen.
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany.
authors.forename: Sarah
authors.initials: S
authors.lastname: Schulz
authors.forename: Marina
authors.initials: M
authors.lastname: Iglesias-Cans
authors.forename: Alexander
authors.initials: A
authors.lastname: Krah
authors.forename: Ozkan
authors.initials: O
authors.lastname: Yildiz
authors.forename: Vanessa
authors.initials: V
authors.lastname: Leone
authors.forename: Doreen
authors.initials: D
authors.lastname: Matthies
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Cook
authors.forename: José D
authors.initials: JD
authors.lastname: Faraldo-Gómez
authors.forename: Thomas
authors.initials: T
authors.lastname: Meier
mesh_terms: D020816:Amino Acid Motifs; D001665:Binding Sites; D055162:Biocatalysis / Q000187:drug effects; D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology*; D018360:Crystallography, X-Ray; D003902:Detergents / Q000494:pharmacology; D004024:Dicyclohexylcarbodiimide; D016967:Fusobacterium nucleatum / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007476:Ionophores / Q000494:pharmacology; D007477:Ions; D007700:Kinetics; D008094:Lithium / Q000378:metabolism; D025261:Mitochondrial Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D011522:Protons; D012964:Sodium / Q000378:metabolism*; D013379:Substrate Specificity / Q000187:drug effects
chemical_list: D003902:Detergents; D007476:Ionophores; D007477:Ions; D011522:Protons; D004024:Dicyclohexylcarbodiimide; D008094:Lithium; D012964:Sodium; C474451:F1F0-ATP synthase; D025261:Mitochondrial Proton-Translocating ATPases